Demountable coaxial connectors



Dec. 27, 1960 J BIRD ETAL 2,966,645

DEMOUNTABLE COAXIAL CONNECTORS Filed June 15, 1956 46 INV EN TORS.

James 2 Bird Henry J Calder/lead F 5 Herbert H. Heller nite States I DEMOUNTABLE COAXIAL CONNECTORS Filed June 13, 1956, Ser. No. 591,236

12 Claims. (Cl. 333-97) This application is a continuation in part of co-pending application, Serial No. 490,334, filed February 24, 1955, now Patent 2,891,221, dated June 16, 1959, for Standing Wave Indicator.

This invention relates to electrical systems for indicating or measuring high frequency wave signals or wave energy, mainly the measurement or detection of such wave signals or energy propagated along a tubular transmission line, especially a coaxial transmission line, and to the mode of operation, to the construction, and to the combination and connection of parts of components in such systems.

In such apparatus various types of coaxial line elements or transmission line units are employed designed to be inter-conected by universal connectors or fittings. However, several different types of universal connectors are in use and, moreover, it is sometimes desired to reverse a transmission line unit end for end, or to provide socket type connectors at both ends, or plug type connectors at both ends in order that a socket type connector may be provided where needed to mate with a plug type connector or vice-versa.

Accordingly, it is an object of the invention to provide interchangeable end connectors and to provide a concentric line insertion device with interchangeable connector fittings such that the device may be inserted in concentric lines of different diameters and with different types of connection fittings without disturbing or changing the internal arrangement of construction of the insertion device.

Further objects and advantages pertaining to certain novel features of construction and combinations and arrangements of parts are apparent in the following detailed description of embodiments of the invention, this description being made in connection with the accompanying drawings forming a part of the specification.

In the drawings:

Fig. 1 is an elevational view, partially diagrammatic, partially in section and with parts broken away, of a high frequency electrical system incorporating a directional coupler embodying the principles of the invention claimed in the parent application and constituting an insertion type of wattmeter or standing wave ratio indicator for use in a coaxial transmission line and having interchangeable end connectors;

Fig. 2 is an end view of the apparatus of Fig. l drawn to a somewhat enlarged scale, partially broken away, and partially in section, represented as seen by looking in the direction of the arrows 2-2 shown in Fig. 1;

Fig. 3 is an exploded fragmentary view of a longitudinal section through one end of the apparatus of Fig. 1; and

Figs. 4 and 5 are fragmentary views in section corresponding to Fig. 3, illustrating modified forms of end connectors.

Like reference characters are utilized throughout the drawings to designate like parts.

The directional coupler shown in the drawings is an illustrative embodiment of coaxial line apparatus in which atet 2,66,645 Patented Dec. 2'7, 196i of interchangeable end connectors, in accordance with the invention, permits the incorporation of such an insertion device in high frequency electrical transmission lines regardless of the type of connectors or fittings employed therein.

As there shown the device or system includes a short section of transmission line L comprising a metal outer conductor 1 in the form of a cast metal tube of brass or the like and a coaxial inner conductor 10. The tube has a smooth internal cylindrical surface 2 in the ends of which insulator bushings composed of polytetrafiuoroethylene 3 and 3a are fitted. The bushings 3 and 3a are provided with internal bores 4 of a suitable size to receive reduced diameter ends 5 of the center conductor 19, which is thereby centered axially in the tubular outer conductor 1. The internal cylindrical surface 2 of the outer conductor 1 and the rod-like inner conductor 10 comprise a coaxial line section having a characteristic impedance corresponding to that of the coaxial transmission line in which the device or system is inserted. As here shown, the characteristic impedance is approximately 50 ohms, the proportioning of the parts being conventional to obtain the desired impedance and to avoid objection-' able reflections.

On the ends of the outer conductor 1 are mounted connector fitting assemblies for attaching the device to or between the ends of conventional coaxial lines. As shown at the left end of Fig. l and in Fig. 3, there is a female end fitting assembly comprising a tubular metal element 6 conveniently made in the form of a turning of brass or the like. Each of the tubular fitting elements is formed at one end with a circular external rabbet so as to be re ceived within the center circular opening of an attaching element or flange plate 7 also of brass or the like. The tube 6 is brazed or silver-soldered into the opening in the attaching plate and, of course, is rigid therewith. If desired, the tube and attaching plate may be formed in one piece as an integral unit. In outline form this attaching plate 7 corresponds to the respective ends of the conductor body 1, being here subtantially square as shown in Fig. 2. Cap screws 9 are received through openings 8 in the corners of the attaching plates 7 and are threaded into the conductor body 1, to draw the end connector fitting plate 7 snugly against the flat end face of the body 1 to establish a strong physical and a good electrical connection around the entire circumferential extent of the internal circular conductor surface 2.

An external thread 11 on the outer end of the connector fitting element 6 is adapted to receive the conventional coupling collar (not shown) carried on the end of the coaxial transmission line to which the unit I. is to be connected or in which it is to be inserted.

For connection of the ends of the center conductor 10 to the center conductor or conductors of the transmission line or lines in which the device is inserted, the following arrangement is employed as part of the connector fitting assembly feature.

The conductor iii is formed with axial bores 14 in its ends to receive tapering inner ends 13 of terminal rods or pins 12. Each of these pins is held in a tubular insulator or insulating sleeve 18 of stiff plastic material such as polytetrafiuoroethylene received against a shoulder 16 as by a press fit in a cylindrical bore 23 in the end fitting element 6. Good electrical connections are accomplished by slitting the inner end 13 of the connectar pin 12 so that the pin end has a spring fit in the end bore 14. The outer end 15 of the connector pin 12 is also slotted and formed with an axial bore to receive and yieldingly spring grip the terminal pin of a conventional coaxial line end fitting as the latter is pressed into the tapered outer end openings 24 of the connector element 6.

The cylindrical opening 23 that receives the tubular insulator 18 at the inner end of the connector element 6 is formed by a counterbore which forms an annular ridge 25 and provides the circular radial shoulder 16 in the middle of the tubular element, this shoulder constituting a seat for locating the plastic insulator tube 18 in assembly. The insulator tube 18 that supports the connector pin 12 is of greater axial length than the cylindrical counterbore 23 in which it is received. The portion of each insulator 18 that projects beyond the plane of the base flange 7 is of reduced diameter, as indicated at 19, being received within the bore 4 of insulator bushing 3 and being abutted against the end of the reduced diameter portion of the inner conductor 10. The formation of the reduced diameter end portion 19 on the insulator 18 provides also a radial shoulder 17 in the plane of the end face of the connector fitting assembly. The shoulder 17 abuts the end face of the insulator bushing 3 about the opening 4. The ends of the reduced diameter portions 5 of the center conductor are spaced axially from the planes of the adjacent circular end openings in the outer conductor 1. Such axial offsets improve the transition, since the step down to the diameter of the pin 12 at each end is thus axially spaced from the plane of the step down in the outer conductors. Likewise the transition from the annular plastic bushing 3 to the air dielectric in the space surrounding the center conductor 10 may in certain instances be improved by a short axial extension or collar 22 shown at the left of Fig. l on the plastic insulator bushing 3, the extension being of the same outer diameter as the center conductor and eing abutted endwise on the shoulder 21 formed on the center conductor by the reduced diameter end portion 5, as shown. in Fig. 3 and in the left hand end of Fig. 1. However, the invention is not limited thereto as the desired transition effect may also be obtained by leaving a recess 28 shown at the right of Fig. 1 between the shoulder 21 formed in the center conductor 1t? and the annular bushing 3a from which the extension 22 has been omitted.

By reason of a strong frictional grip on the outer periphery of the insulator bushing 3 by the cylindrical surface 2 of the outer conductor, it is feasible to remove and replace either one or both of the connector end fitting assemblies without disturbing relationship between the center conductor 18 and the outer conductor or the coaxial line. Removal of one of the fitting assemblies is accomplished by withdrawing the holding screws 9, permitting the attaching plate 7, the tubular clear it 6, the connector pin 12 and the insulator 13 to be removed as a unit.

Thus, the end fitting assemblies (or one of them) are readily removable for replacement by a different type of fitting assembly or a fitting assembly of a difierent diameter or configuration.

The fittings can be supplied readily in different sizes and kinds of plug or socket connectors for use in adapting the insertion sampling device to coaxial transmission lines having different kinds and types of end fittings of difierent sizes, the substitution being facilitated by the interfitting spring pin-socket arrangement of the center conductor pin 12 carried by the insulator bushing of the outer tubular element 6. In the removal and replacement of the end fitting assemblies, or one of them, no rotation or turning of one combined part relative to the other is necessary, since the parts are brought together readily or separated by simple rectilinear move- 4 ments. Such removal of the end fitting does not interfere with the adjustment or setting of any of the other parts or components of the instrument assembly, since the rigid insulator bushing 3 holds the center conductor 10 in fixed relationship to the outer conductor 1 during the removal and replacement of an end fitting assembly.

As illustrated in Fig. 1 at the right hand end, a plug connector may be substituted for a socket connector. No change in conformation of the end 5 of the center conductor 10 or of the insulator tube 18 is required. Instead of a center conductor pin 12 with a split outer end, a connector pin 26 is utilized having a conical tip 27. The inner end 13 is like that of the pin 12 for spring fit in the end bore 14 of the rod 10. Instead of an externally threaded tube 6, a tubular conductor 28 is joined to the attachment flange 7, and formed with a slotted sleeve contact 29 for resilient connection with the outer terminal of a coaxial socket connector. A conventional coupling nut 31 is also provided, having a spring ring 30 for rotatably securing it in the tubular fitting 28.

The interchangeable connector arrangement lends itself also to optional selection of different types of connectors for diiferent purposes or to connection with transmission lines having special types of fittings. For example, an HN type of connector may be substituted as illustrated in Fig.4. i

The connection illustrated in Fig. 4 comprises an insulator bushing 32 mounted in a tubular fitting 33, secured therein by a locking pin 34. The tubular fitting 33 is joined to a square flange attaching plate 7 as in the arrangements of Figs. l3. A center conductor terminal rod or pin is held within the insulator bushing 32 by a press fit taking the form either of a socket connector such as the rod 12 in Fig. 3 or a plug connector rod 26 as illustrated. The end of the tubular fitting 33 is provided with slots as shown at 35 to form a resilient contact with a socket type outer-conductor connector. The insulator 32 has a corona-blocking skirt portion 36. The fitting 33 may be formed with a reduced diameter throat 37 surrounding a neck portion 38 of the insulator 32.

Still another type of connector which may readily be substituted is the toothed-end contact type illustrated in Fig. 5, which may have either plug or socket type center conductor connection. As illustrated, there is a metallic sleeve 41 with a tubular fitting 42 joined thereto having external threads 43, and providing a shoulder 44 for locating a stepped-diameter insulator bushing 45.

The annular end 46 of the fitting 42 is formed with scallops 47 or blunt teeth to make abutting contact with a mating fitting.

The center conductor pin fitting comprises a rod 48 having a slotted end 49 and a smaller-diameter stem 51, with a slotted-spring socket contact 52 soft-soldered to the stem 51. The spring contact 52 is formed with a stepped-diameter base 53 around the stem 51 providing a shoulder 54. A washer 55 is provided, which surrounds the stem 51 and rests against a shoulder 56 in the rod 48. The bushing 45 is provided with a throat 57 of reduced bore against which the Washer 55 and the shoulder 54 rest to locate the center-conductor fitting.

In accordance with the patent statutes the principles of the present invention may be utilized in various ways, numerous modifications and alterations being contemplated, substitution of parts and changes in construction being resorted to as desired, it being understood that the embodiments shown in the drawings and described above and the particular method set forth are given merely for the purpose of explanation and illustration without intent to limit the scope of the claims to the spacefic details disclosed.

What we claim and desire to secure by Letters Patent of the United States is:

1. In combination a hollow conductor, insulator means supported therein at the endthereof, having a bore, a

central conductor having a reduced diameter end portion and a greater diameter central portion with a shoulder at the junction of the two portions, said reduced diameter end resting in said insulator bore with its shoulder spaced axially from the insulator means a distance less than the radial depth of such shoulder to form a length of coaxial transmission line, an interchangeable connector fitting with means for securing it to the end of said hollow conductor and having a tubular projecting portion, and a terminal rod received within said insulator bore projecting through the tubular projecting portion of the connector fitting at one end and at the other end contacting the end of said central conductor whereby a mating coaxial line connector may be connected to said projecting tubular portion and to the said terminal rod for electrically connecting a coaxial transmission line to said hollow conductor and said central conductor.

2. In combination in a high frequency electrical system, a coaxial line structure comprising a tubular outer conductor having a cylindrical bore and a flat end face normal to the bore axis, a central conductor extending through the outer conductor in coaxial relation and separated therefrom by an annular dielectric space, the central conductor having an end face spaced axially inwardly from the plane of the fiat face, an annular insulator in one portion of said space, said insulator having an end face coplanar with said fiat face and a central opening, the central conductor being received in said opening; a coaxial line terminal comprising a flat faced conductive plate having an opening, a conductive tube fast to the plate and projecting from one side thereof, a terminal rod, and a tubular insulator surrounding the rod and supporting the latter within the conductive tube in coaxial relation; means securing the line terminal to the line structure in predetermined position for removal and replacement and with the flat face of the plate against the end faces of both the tubular conductor and the annular insulator; the terminal rod and the tubular insulator of the positioned line terminal both projecting axially beyond said plate face and into the opening in the end face of the annular insulator with the rod coaxial to and in electrical contact with the central conductor; one of the conductors of the line structure being formed with a stepped portion which receives the annular insulator, and said annular dielectric space including another portion contiguous to the one portion, of greater axial length and of less radial dimension than said one portion.

3. In combination a tubular outer conductor having a conductive internal wall of circular section, an insulator supported therein at one end, said insulator having axially spaced radial faces and a central through bore, a stepped diameter center conductor within the hollow conductor and having a reduced end portion and a relatively greater central portion with a radial shoulder at the junction of such portions, said reduced end portion being disposed in said bore, the central portion of the center conductor being separated from the outer conductor adjacent one face of the insulator by an annular fiuid dielectric space, said insulator having an annular projection extending axially from said one face and surrounded by a portion of the dielectric space, said projection closely embracing the reduced end portion of the center conductor and abutting against the junction shoulder to form a length of coaxial electrical transmission line with improved transitional electrical characteristics, a connector fitting having an electrical conductive body, means securing said fitting to the end of said tubular conductor, said fitting body being in electrical contact with the tubular conductor and having a tubular projecting portion, and a terminal rod projecting axially through the tubular portion of the connector body and at one end contacting said center conductor, whereby a mating standard coaxial line end fitting may be connected to said projecting tubular portion of the fitting body and to the other end of said terminal rod 6 for electrically connecting a coaxial transmission line to said tubular and center conductors.

4. In combination, a coaxial electrical line unit comprising a tubular conductor having an internal chamber with a conductive wall of circular section and an end face extending radially fro-m a circular junction with the conductive wall in a plane normal to the chamber axis, a center conductor, and insulating means in the chamber embracing the center conductor andsupporting it in coaxial relation to the wall, said insulating means having an end face substantially coplanar with the end face of the tubular conductor, the center conductor being short of and having an end face axially spaced from said plane; a connector assembly and means securing the same on the tubular conductor against the end face of the latter, said connector assembly being adapted to receive detach ably a standard end fitting of a coaxial electrical transmission line for effecting electrical connection of central and outer conductors of such a line to the center and tubular conductors, respectively, of the line unit, said connector assembly comprising a tubular connector, a terminal rod, and a tubular insulator, the tubular connector having a substantially fiat conductive end face received against the end faces of the tubular conductor and the insulating means and effecting electrical contact with the tubular conductor at said juncture and in said plane, the tubular connector being formed with an internal passage having a cylindrical conductive wall of less diameter than and concentric to the axis of the chamber, said passage having a circular opening through the end face of the connector defined by the juncture of the passage wall and the connector end face, and the insulator supporting the rod in the passage in coaxial relation to the passage wall; the insulator including a portion projecting through said plane and abutting the end face of the center conductor; means holding the insulator in the tubular connector to resist relative axial movement in assembling the connector assembly to the line unit and in detaching such standard end fitting, and the center conductor and the terminal rod having interfitting pin and socket formations on their ends providing an electrical connection substantially in the plane of the end face of the center conductor and spaced axially from the plane of contact between the tubular conductor and the tubular connector to provide good electrical transition between the line unit and the connector assembly.

5. A coaxial electrical line unit and connector assembly combination as defined in claim 4 in which the tubular insulator comprises coaxial cylindrically surfaced portions of different diameters and has an annular radial shoulder at the juncture of said portions abutting the end face of the insulating means.

6. A coaxial electrical line unit and connector assembly combination as defined in claim 4 in which the insulating means comprises an annulus having an axial through opening of circular section and an outer periphery engaging the chamber wall, the central conductor extending into and only part way through such opening in the insulating annulus from one end, the projecting portion of the insulator being of circular section and extending into such opening from the other end, the insulating annulus closely embracing the projecting portion of the insulator, and the abutment of the insulator against the center conductor being in a plane intermediate and spaced axially from the ends of the through opening.

7. A coaxial electrical line unit and connector assernbly combination as defined in claim 4 in which the center conductor comprises a central portion and a cylindrical end portion and has an annular radial shoulder at their juncture, the insulating means comprising an annulus having an inside face spaced axially from its end face and having an axial through opening in which said cylindrical end portion of the center conductor is received, the central portion of the center conductor being separated from the conductive wall of the tubular conductor by a surrounding annularlclearance. and dielectric, space, said insulating means having an annular fiange projecting axially from its inside face and abutted against the radial shoulder of the center conductor, and the axial flange of the insulating means being surrounded by a portion of said annular dielectric space, the axial spacing of the radial shoulder of the center conductor from the inside face of the insulating annulu providing for improved electrical transition between the insulating means and the dielectric space.

8. In combination, a coaxial electrical line unit comprising a tubular conductor having an internal chamber with a conductive Wall of circular section and an end face extending radially from a circular junction with the conductive wall in a plane normal to the chamber axis, a center conductor, and an insulating annulus Within and fitting the wall of the chamber, said insulating annulus having an inner end face and, spaced axially therefrom, an outer end face substantially coplanar with the end face of the tubular. conductor, the center conductor having a central portion and a reduced end portion with a radial shoulder at their juncture, such reduced end projecting into and the radial shoulder abutting the insulating annulus, said reduced end having an end face intermediate and spaced axially from the inner and outer end faces of the insulating annulus and from said plane, a connector assembly and means securing the same on the tubular conductor against the end face of the latter, said connector assembly being adapted to receive detachably a standard end fitting of a coaxial electrical transmission line for effecting electrical connection of central and outer conductors of such a line to the center and tubular conductors, respectively, of the line unit, said connector assembly comprising a tubular connector, a terminal rod, and a tubular insulator, the tubular connector having a substantially flat conductive end face received flatwise against the end faces of the tubular conductor and the insulating annulus and effecting electrical contact with the tubular conductor at said juncture and in said plane, the tubular connector being formed with an internal passage having a cylindrical conductive wall of less diameter than and concentric to the axis of the chamber, said passage having a circular opening through the end face of the connector defined by the juncture of the passage wall and the connector end face, and the insulator supporting the rod in the passage in coaxial relation to the passage wall; the insulator including a portion projecting through said plane and abutting the end face of the center conductor; means holding the insulator in the tubular connector to resist relative axial movement in assembling the connector assembly to the line unit and in detaching such standard end fitting, and the center conductor and the terminal rod having interfitting pin and socket formations on their ends providing an electrical connection substantially in the plane of 'the' end face of the center conductor and spaced axially from the plane of contact between the tubular conductor and the tubular connector to provide improved electrical transition between the line unit and the connector assembly.

9. In combination, a coaxial electrical line unit comprising a tubular conductor having an internal chamber with a conductive wall of circular section and an end face extending radially from a circular junction with the conductive wall in a plane normal to the chamber axis, a center conductor, and insulating means in the chamber embracing the central conductor and supporting it in coaxial relation to the wall, said insulating means having an end face substantially coplanar with the end face or" the tubular conductor, the central conductor being short of and having an end face axially spaced from said plane; a connector assembly and means securing the same on the tubular conductor against the end face of the latter, said connector assembly being adapted to receive detachably a standard end fitting of a coaxial electrical transmission line for effecting electrical connection of central and outer conductors of such a line to the center and tubular conductors, respectively, of the line unit, said connector assembly comprisinga connector member, a terminal rod, and a tubular insulator, the connector member including a conductive plate formed with a central aperture and a tubular element formed withan internal passage,- the element being securedat one end to the plate with its passage registered with the central aperture, the plate having a substantially flat face received fiatwise against the end faces of the tubular conductor and the insulating means and efiecting electrical contact with the tubular conductor at said juncture and in said plane, the internal passage having a cylindrical conductive wall of less diameter than and concentric to the axis of the chamber, said passage having a circular opening through the end face of the connector defined by the juncture of the passage wall andthe connector end face, and the insulator supporting the rod in the passage in coaxial relation to the passage wall; the insulator including a portion projecting through said plane and abutting the end face of the center conductor; means holding the insulator in the connector member to resist relative axial movement in assembling the connector assembly to the line unit and in detaching such standard end fitting, and the center conductor and the terminal rod having interfitting pin and socket formations on their ends providing an electrical connection substantially in the plane of the end face of the center conductor and spaced axially from the plane of contact between the tubular conductor and the plate to provide improved electrical transition between the line unit and the connector assembly.

10. A coaxial electrical line unit and connector as sembly combination as defined in claim 9 in which the securing means comprises a plurality of screws received through the plate and anchored to the tubular conductor at points angularly distributed about said axis and spaced radially outwardly from the tubular element.

11. A coaxial electrical line unit and connector assembly combination as defined in claim 9 in which the terminal rod includes a split end portion which constitutes said pin formation, the split portion projecting axially from and beyond the projecting portion of the insulator, and the center conductor is formed with an' axial bore which constitutes said socket formation, such bore receiving the split portion of the rod telescopically in sliding relation as the connector assembly is assembled to the line unit.

12. in combination, a coaxial electrical line unit comprising a tubular conductor having an internal chamber with a conductive wall of circular section and an end face extending radially from a circular junction with the conductive wall in a plane normal to the chamber axis, a center conductor, and insulating means in'the chamber embracing the center conductor and supporting it in coaxial relation to the wall, said insulating means having an end face substantially coplanar with the end face of the tubular conductor, the center conductor being short of and having an end face axially spaced from said plane; a connector assembly adapted to receive detachably a standard end fitting of a coaxial electrical transmission line for effecting electrical connection of central and outer conductors of such a line to the center and tubular conductors, respectively, of the line unit, said connector assembly comprising a tubular connector, a terminal rod, and a tubular insulator, the tubular connector having a substantially fiat conductive end face received against the end faces of the tubular conductor and the insulating means and eifectingelectrical contact with the tubular conductor at said juncture and in said plane, the tubular connector being formed with an internal passage having a cylindrical conductive wall of less diameter than and concentric to the axis of the chamber, said passage having a circular opening through the end face of the connector defined by the juncture of the passage wall and the connector end face, and the insulator supporting the rod in the passage in coaxial relation to the passage wall; the insulator including a portion projecting through said plane and abutting the end face of the center conductor; means holding the insulator in the tubular connector to resist relative axial movement in assembling the connector assembly to the line unit and in detaching such standard end fitting, the center conductor and the terminal rod having interfitting pin and socket formations on their ends providing an electrical connection substantially in the plane of the end face of the center conductor and spaced axially from the plane of contact between the tubular conductor and the tubular connector to provide a good electrical transition between the line unit and the connector assembly, and a plurality of screws distributed angularly about and spaced radially from said axis and securing the connector assembly to the line unit for facile removal and replacement and collectively being adapted to draw together strongly the end faces of the tubular conductor and the tubular connector in establishment of good electrical contact.

References Cited in the file of this patent UNITED STATES PATENTS 1,376,735 Stalhane et al. May 3, 1921 2,449,073 Johannesen Sept. 14, 1948 2,552,414 Eriksen et al. May 8, 1951 2,641,744 De Packh et a1 June 9, 1953 2,754,487 Carr et al. July 10, 1956 2,762,025 Melcher Sept. 4, 1956 FOREIGN PATENTS 568,596 Great Britain Apr. 12, 1945 

